Re: [Please Help] How to get coefficient list from a

*To*: mathgroup at smc.vnet.net*Subject*: [mg114457] Re: [Please Help] How to get coefficient list from a*From*: =?tis-620?b?zdTKw+zD0aqq7CCiqMPD2OinyA==?= at smc.vnet.net*Date*: Sun, 5 Dec 2010 21:49:21 -0500 (EST)

>From previous equation, I want to know if i want to change the value in p[i,k-i] into sets of coefficient. How to do that? Any hint is greatly appreciated. kajornrungsilp.i at gmail.com> wrote: > Thank you for all of your answer. I very appreciate you. but i have some > question that i confuse in my code. > My code is > n == 4; > u1 == Normal[ > Series[u[Ca[t], T[t]] - u[3.2066, 317.5529], {Ca[t], 3.2066, > n}, {T[t], 317.5529, n}]] > d == {}; > q[0] == {}; > For[k == 1 , k <== n - 1, k++, > For[i == 0 , i <== k , i++, > p[i, k - i] == (i!*(k - i)!)* > SeriesCoefficient[u1, {Ca[t], 3.2066, i}, {T[t], 317.5529, k - i}]; > q[k] == Union[q[k - 1], p[i, k - i]]; > d==Union [d,q[k]]; > ]]d > I want to know,why it doesn't collect the coefficient of my equation? what > is something wrong in my code? > > Best Regard. > > Bob Hanlon <hanlonr at cox.net> wrote: > > A simpler form: >> >> expr1 == a1 + a2*x + a3*y + a4*x^2 + a5*x*y + a6*y^2; >> >> myCoef[expr_, var_List] :== >> SortBy[List @@ expr1, Total[Exponent[#, var]] &] /. Thread[var -> 1] >> >> myCoef[expr1, {x, y}] >> >> {a1, a2, a3, a4, a5, a6} >> >> >> Bob Hanlon >> >> ---- Bob Hanlon <hanlonr at cox.net> wrote: >> >> ========================== >> >> expr1 == a1 + a2*x + a3*y + a4*x^2 + a5*x*y + a6*y^2; >> >> Since you apparently want to ignore zero coefficients then this extracts >> the non-zero coefficients >> >> (List @@ expr1) /. {x -> 1, y -> 1} >> >> {a1, a2, a4, a3, a5, a6} >> >> However, this standard ordering is different from yours. Presumably, your >> ordering is >> >> myCoef[expr_, var_List] :== Module[ >> {coef == (List @@ expr) /. Thread[var -> 1]}, >> Last /@ Sort[ >> Cases[List @@ expr, >> a_?(MemberQ[coef, #] &)*z_. -> >> {Total[Exponent[z, var]], a}]]]; >> >> myCoef[expr1, {x, y}] >> >> {a1, a2, a3, a4, a5, a6} >> >> >> Bob Hanlon >> >> ---- <kajornrungsilp.i at gmail.com> wrote: >> >> ========================== >> Thank you for your answer. But I would like only the coefficient of series >> equation in the form {a1, a2 , a3 ,a4,a5,a6} not to be in the form of >> {{a1, >> a3, a6}, {a2, a5, 0}, {a4, 0, 0}}. How to get there? >> Best regard >> >> >> 2010/12/3 Bob Hanlon <hanlonr at cox.net> >> >> > >> > expr1 == a1 + a2*x + a3*y + a4*x^2 + a5*x*y + a6*y^2; >> > >> > coef == CoefficientList[expr, {x, y}] >> > >> > {{a1, a3, a6}, {a2, a5, 0}, {a4, 0, 0}} >> > >> > From example in documentation on CoefficientList >> > >> > expr2 == Fold[FromDigits[Reverse[#1], #2] &, coef, {x, y}] >> > >> > a1 + a2 x + a4 x^2 + (a3 + a5 x) y + a6 y^2 >> > >> > expr1 ==== expr2 // Simplify >> > >> > True >> > >> > >> > Bob Hanlon >> > >> > ---- Autt <kajornrungsilp.i at gmail.com> wrote: >> > >> > ========================== >> > Greeting, >> > I've a list issued from multivariate series like : K=={a1+a2*x +a3*y >> > +a4*x^2*+a5*x*y +a6*y^2 } >> > I need to have {a1, a2 , a3 ,a4,a5,a6} >> > >> > How to do that please? >> > e.g. >> > n == 3 >> > u == Normal[Series[x^4 + y^4 + x^2, {x, 5, n}, {y, 5, n}]] >> > c[0] == {}; >> > d == {}; >> > q[0] == {}; >> > For[k == 1 , k <== n - 1, k++, >> > For[i == 0 , i <== k , i++, >> > p[i, k - i] == >> > SeriesCoefficient[u, {x, 5, i}, {y, 5, k - i}]; >> > q[k] == Union[{q[k - 1], {p[i, k - i]}}]; >> > d == Union[d, q[k]]; >> > >> > Print[d]; >> > >> > Best regard, >> > >> >> >